1. Field of the Invention
The present invention relates to a storage medium and a semiconductor package.
2. Description of the Related Art
In a storage medium that includes a semiconductor package and a mounting substrate on which the semiconductor package is mounted, it has been desired to further downsize the storage medium with a larger capacity. Conventionally, as one of the methods for realizing downsizing storage mediums with a larger capacity, there has been proposed the use of a semiconductor package of various types such as a ball grid array (BGA) and a land grid array (LGA).
In a BGA semiconductor package or LGA semiconductor package, unlike a semiconductor package of a thin small outline package (TSOP), electrodes are arranged on the bottom surface of a resin encapsulation, and thus the electrodes (leads) do not extend from the periphery (end surface) of the resin encapsulation. At the time of mounting on the mounting substrate, the resin encapsulations of the adjacent packages can be placed close to each other, and this can achieve a high density of a semiconductor chip and downsizing of a storage medium. Conventionally, to achieve a higher density of the semiconductor chip, there has been also proposed a semiconductor package of a multi chip package (MCP) in which a plurality of semiconductor chips are stacked and encapsulated in a single package.
In such a semiconductor package, while it is possible to achieve a high density thereof and downsizing of the storage medium, a large number of electrodes are placed on the bottom surface of the resin encapsulation. The large number of electrodes formed on the bottom surface of the resin encapsulation are generally formed in a rectangular grid shape. However, to improve the reliability, the electrodes formed at the corners in the array are not used for transferring and receiving a signal. This is because cracks can be easily generated at the corners of the package (for example, see Japanese Patent Application Laid-open No. 2007-207397).
However, a storage medium on which such a semiconductor package is mounted has been desired to have a higher reliability. Recently, a storage medium in which a non-volatile semiconductor memory is incorporated has been used in various areas ranging from large-scale computers to personal computers, household appliances, cellular phones and the like. Further, such a storage medium is even considered as an alternative to a hard disk drive (HDD). Therefore, a more reliable storage medium with excellent impact resistance and temperature cycle resistance has been desired.